1. Field of the Invention
The present invention relates to a graph display apparatus for calculating the graph of a functional formula or the like, and displaying the calculated graph and, more particularly, to a graph display apparatus comprising a display unit for simultaneously displaying the graphs of a plurality of functional formulas on a single X-Y coordinate system or different X-Y coordinate systems.
2. Description of the Related Art
A graph display apparatus, which, by inputting a functional formula Y=f(x), e.g., Y=X.sup.2, and designating display ranges of X and Y, displays the graph of Y=X.sup.2 within the designated ranges on the X-Y coordinate system, has been commercially available, and such a technique is described in, e.g., U.S. Pat. No. 4,794,553 and U.S. Pat. No. 4,794,554. Some graph display apparatuses of this type have a function of simultaneously displaying the graphs of a plurality of functional formulas on a single X-Y coordinate system. When the graphs of a plurality of functional formulas are simultaneously displayed on a single X-Y coordinate system, all the functional formulas have the same display range, and it is impossible to display functional formulas with different display ranges in comparison with each other.
When the graphs of functional formulas are displayed, the functional formulas often have different coordinate systems. For example, as the coordinate systems, orthogonal coordinates, polar coordinates, parameter coordinates, and the like are used in correspondence with different functional formulas. These different coordinate systems must be independently displayed.